Hydrocarbons, such as fossil fuels (e.g. oil) and natural gas, are extracted from underground wellbores extending deeply below the surface using complex machinery and explosive devices. Once the wellbore is established by placement of casing pipes after drilling, a perforating gun assembly, or train or string of multiple perforating gun assemblies, are lowered into the wellbore, and positioned adjacent one or more hydrocarbon reservoirs in underground formations.
Assembly of a perforating gun requires assembly of multiple parts. Such parts typically include a housing or outer gun barrel. An electrical wire for communicating from the surface to initiate ignition, a percussion initiator and/or a detonator, a detonating cord, one or more charges which are held in an inner tube, strip or carrying device and, where necessary, one or more boosters are typically positioned in the housing. Assembly of the perforating gun typically includes threaded insertion of one component into another by screwing or twisting the components into place. Tandem seal adapters/subs are typically used in conjunction with perforating gun assemblies to connect multiple perforating guns together. The tandem seal adapters are typically configured to provide a seal between adjacent perforating guns. Some tandem seal adapters may be provided internally or externally between adjacent perforating guns, which, in addition to requiring the use of multiple parts or connections between the perforating guns, may increase the length of each perforating gun and may be more expensive to manufacture. One such system is described in PCT Publication No. WO 2015/179787A1 assigned to Hunting Titan Inc.
The perforating gun includes explosive charges, typically shaped, hollow or projectile charges, which are initiated to perforate holes in the casing and to blast through the formation so that the hydrocarbons can flow through the casing. The explosive charges may be arranged in a hollow charge carrier or other holding devices. Once the perforating gun(s) is properly positioned, a surface signal actuates an ignition of a fuse or detonator, which in turn initiates a detonating cord, which detonates the explosive charges to penetrate/perforate the casing and thereby allow formation fluids to flow through the perforations thus formed and into a production string. Upon detonation of the explosive charges, debris typically remains inside the casing/wellbore. Such debris may include shrapnel resulting from the detonation of the explosive charges, which may result in obstructions in the wellbore. Perforating gun assemblies may be modified with additional components, end plates, internal sleeves, and the like in an attempt to capture such debris. U.S. Pat. No. 7,441,601 to GeoDynamics Inc., for example, describes a perforating gun assembly having an inner sleeve configured with pre-drilled holes that shifts in relation to an outer gun barrel upon detonation of the explosive charges in the perforating gun, to close the holes formed by the explosive charges. Such perforating gun assemblies require numerous components, may be costly to manufacture and assemble, and may reduce/limit the size of the explosive charges, in relation to the gun diameter, which may be compatible with the gun assembly.
There is a need for an improved perforating gun assembly that does not require the use of tandem seal adapters or tandem subs to facilitate a sealed connection between perforating gun assemblies. There is a further need for a perforating gun assembly that includes an efficient design for capturing debris resulting from detonation of a plurality of shaped charges.